Combined effects of temperature and diet on growth and biochemical composition of the Pacific oyster Crassostrea gigas (Thunberg) spat

Temperature and quality of the available food are important factors that influence the physiology of oysters; however, the combined effects have not been well studied. We evaluated the impacts of the temperature and diet on the growth, survival and biochemical composition in the Pacific oyster Crassostrea gigas spat, cultured in the laboratory for 8 weeks at 23, 26, 29 and 32°C and fed Isochrysis sp.‐Pavlova lutheri (IP) and Dunaliella tertiolecta (Dt). The growth and biochemical composition showed a pattern, which changed in response to rising temperature. The shell length was significantly longer, in spat fed the IP diet, except at 32°C, where both diets produced poor growth results. The survival was <50% after 5 weeks at 32°C, whereas at all other temperatures it was >88%. High temperatures directly increased lipids and saturated fatty acids, while the proteins, carbohydrates and unsaturated fatty acids decreased. High temperatures achieved in the environment, as those reached on clear summer days during low tides, are an important stressor in oyster spat, especially when the quality of the available food is poor.     

Insights into Insulin and Glucagon Responses in Fish

The focus of this review is the response of insulin and glucagon to various experimental and physiological conditions in fish. Circulating levels of insulin and glucagon have been analyzed in several fish species, principally salmonids. It is generally accepted that, in fish, the insulin secretion in response to amino acids is stronger than to glucose, although this information has been obtained mainly from carnivorous species. Studies of other species demonstrate that the alimentary pattern affect hormonal secretion and should be taken into account when the effects of secretagogues are analyzed. There are few studies of glucagon secretion, even in salmonids, although it is known that amino acids also stimulate its release. The level of this response and its relationship to insulin secretion depends upon the species of fish. We will discuss the significance of these observations, while also considering other important factors, including the influence of neuropeptides and interactions with other pancreatic and gastro-intestinal hormones. Finally, seasonal, temperature and reproductive stage effects will be discussed, all of which should be taken into account when attempting to understand the role of pancreatic hormones in fish. This short review will not cover the action of these hormones on their target tissues.     

Evolution under domestication of correlated characters in populations of Stenocereus stellatus (Pfeiff.) Riccob., under different forms of management in central Mexico: genetic diversity,damage, and defense mechanisms

Genetic Resources and Crop Evolution - Across the process of domestication, human selection produces changes in target attributes as well as changes that are not necessarily desired by humans due...     

Geographical distribution of the DL1 and DL2 genes causing hybrid dwarfism in Phaseolus vulgaris L., their association with seed size,and their significance to breeding

Summary Dwarlism in F₁ hybrids has been observed in over 100 crosses of dry beans (Phaseolus vulgaris L.) at the Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia. In each cross, one parent always had small seeds and the other parent either medium or la ge ones. This apparent incompatibility between the two groups of germplasm was controlled by two complementary, dominant genes: DL₁ and DL₂. Smallseeded bean lines carried gene DL₁ and originated in Brazil, Colombia, Guatemala, and Mexico; medium for large-seeded bean lines carried gene DL₂ and were from Bolivia, Brazil, Chile, Colombia, Turkey, The United States, and West Germany. Thes two genes have probably played an important role in the evolution of dry bean forms of different seed sizes by serving as a genetic barrier or isolating mechanism, thus limiting free genetic recombination between the two germplasm groups.Apparent differences in the adaptiveness and yielding ability of the two groups of bean germplasm, smallys, medium- and large-seeded, and some breeding implications for manipulation of the genes causing F₁ hybrid dwarfism were also discovered.     

Effect of plant density on selection for seed yield in two population types of Phaseolus vulgaris L.

Summary Pedigree selection for seed yield, using early generation yield tests, was practiced from the F₂ to F₇ in two populations of common bean (Phaseolus vulgaris L.) in three plant densities: 66, 133, and 266 thousand plants ha^-1 at CIAT-Palmira, Colombia. The six highest yielding lines selected from each plant-density, along with 13 parents, were evaluated in a 7×7 lattice design with three replications at the three densities utilized for selection, and at 399,000 plants ha^-1 in 1988 and 1989.Based on the mean performance of selected lines and the mean of the parents, selection for seed yield was effective in all densities in both populations. However, none of the lines selected from the population within the race Mesoamerica (TC 4673) significantly outyielded their best parent under any plant density. The highest yielding lines selected from the interracial population (TR 4635) outyielded their best parent irrespective of the plant-density used for selection. The highest yielding line originated from the highest density used for selection. Low density was neither good for selection nor for evaluation and identification of high-yielding cultivars of common bean. There was no significant difference between the mean yield of lines selected at the intermediate and high population densities. The effects of plant density, year, and their interactions were significant for seed yield.     

Nutrient Loading by Precipitation in the Maracaibo Lake Basin, Venezuela

Nutrient content and pH of rain samples collected at nine sites during 1988-1996 were studied to determine the amounts of N, P and S added by precipitation over Maracaibo Lake basin. The basin is a wide depression occupied by Lake Maracaibo and extensive alluvial plains and delimited by a mountainous zone of variable physiolgraphic characteristics with different cattle ranching and industrial activities. Rain pHs averaged ≈ 4 to 6, individual samples occasionally reached as low as pH 3 in the south basin. NH₄ ⁺ levels were significantly higher (up to 2.6 mg/l NH₄-N) than NO₃ ^? plus NO₂ ^?. Phosphorus levels were low, ranging from undetectable to 1.5 mg/l. The amounts of inorganic N/ha/yr added ranged from ≈ 5.4 Kg in the north to ≈ 8 Kg in the south basin; around the lakeshore, it was estimated that ≈ 9.8–16.8 Kg TN/ha (≈ 55 % as organic-N) are annually deposited. The annual amounts of SO₄-S/ha added range from ≈ 10 to 13 Kg. The contribution of precipitation to P in the ecosystem is very small; ≈ 0.02 – 0.8 Kg of PO₄-P/ha/yr was added in basin. The results of this study show that precipitation represents a significant factor for the total nitrogen and sulfur loading to Maracaibo Lake Basin.     

Vitamin E composition of walnuts (Juglans regia L.): a 3-year comparative study of different cultivars

The tocopherol and tocotrienol composition of walnuts (Juglans regia L.) was determined for nine cultivars (cvs. Arco, Franquette, Hartley, Lara, Marbot, Mayette, Mellanaise, Parisienne, and Rego). Walnuts were harvested over three consecutive years from two different geographical origins (Bragan?a and Coimbra, Portugal), for a total of 26 samples. The methodology employed was a normal-phase high-performance liquid chromatography coupled to a series arrangement of a diode array detector followed by a fluorescence detector, allowing the simultaneous analysis of all tocopherols and tocotrienols. The analyses showed that all samples presented a similar qualitative profile composed of five compounds: alpha-tocopherol, beta-tocopherol, gamma-tocopherol, delta-tocopherol, and gamma-tocotrienol. gamma-Tocopherol was the major compound in all samples, ranging from 172.6 to 262.0 mg/kg, followed by alpha- and delta-tocopherols, ranging from 8.7 to 16.6 mg/kg and from 8.2 to 16.9 mg/kg, respectively. Multivariate analysis of the data obtained showed the existence of significant differences in composition among cultivars. These differences were also significant when cultivars were grouped by year of production, showing that besides genetic factors, the vitamin E composition was influenced by environmental factors.     

Chemical composition and glycemic index of Brazilian pine (Araucaria angustifolia) seeds

The seeds of Parana pine (Araucaria brasiliensis syn. Araucaria angustifolia), named pinh?o, are consumed after cooking and posterior dehulling, or they are used to prepare a flour employed in regional dishes. Native people that live in the South of Brazil usually consume baked pinh?o. As a result of cooking, the white seeds become brown on the surface due to the migration of some tinted compounds present in the seed coat. In this work, the proximate composition, minerals, flavonoids, and glycemic index (GI) of cooked and raw pinh?o seeds were compared. No differences in moisture, lipids, soluble fiber, and total starch after boiling were found. However, the soluble sugars and P, Cu, and Mg contents decreased, probably as a consequence of leaching in the cooking water. Also, the boiling process modified the profile of the phenolic compounds in the seeds. No flavonols were detected in raw pinh?o seeds. The internal seed coat had a quercetin content five times higher than that of the external seed coat; also, quercetin migrated into the seed during cooking. The internal seed coat had a high content of total phenolics, and seeds cooked in normal conditions (with the seed coat) showed a total phenolics content five times higher than that of seeds cooked without the seed coat. Cooking was then extremely favorable to pinh?o seeds bioactive compounds content. The carbohydrate availability was evaluated in a short-term assay in humans by the GI. The GI of pinh?o seeds cooked with the coat (67%) was similar to that of the seeds cooked without a coat (62%) and lower than bread, showing that cooking does not interfere with starch availability. The low glycemic response can be partly due to its high content of resistant starch (9% of the total starch).     

Effect of olive ripeness on the oxidative stability of virgin olive oil extracted from the varieties picual and hojiblanca and on the different components involved

The initial stability of virgin olive oil depends on various factors, among which are the variety and the degree of fruit ripeness. The former, which genetically determines the composition of the olive and its oil, also marks, to some extent, its stability. However, oil stability changes as the olive ripens, so it is obvious that the degree of ripeness is an important factor. The oils were obtained by the Abencor system. Acidity, peroxide index, UV absorption at 232 and 270 nm, sensory analysis, fatty acid composition, tocopherols, phenolic compounds, orthodiphenolic compounds, sterols, pigments, and oxidative stability were determined, and the results were analyzed statistically. During ripening there was a decrease in all of the parameters studied except linoleic acid, Delta-5-avenasterol, and oil content, which increased. Virgin oils showed very good correlation between stability and the concentrations of total phenols, o-diphenols, tocopherols, chlorophyll pigments and carotenoids, linoleic and linolenic acids, total sterols, beta-sitosterol, and Delta-5-avenasterol.     

Rapid determination of inorganic and methyl mercury in fish

A method has been developed that uses a mixed solution of NaOH, NaCl and cysteine to digest fish. Inorganic Hg and MgHg were determined by cold vapor atomic absorption (CVAAS) using a selective reduction step with SnCl₂ and SnCL₂-solutions. Ethyl alcohol was satisfactorily used to prevent excessive foaming. Two optimum digestion procedures were established: (1) using a dry block heater at 90 °C for 1 hr and (2) overnight digestion at 25 to 30 °C. Differences between both were not significant (95%) in the range of 30 to 500 ng g^?1 Hg (II) and MeHg in fish. Reduction of the Hg signal due to matrix effects in different fish species was evaluated (95 to 60%). Oily fish, shrimp and lobsters gave the highest reduction. Internal calibration by addition of Hg standards are strongly recommended when exact determinations are needed. The detection limit obtained was near 10 ng g^?1. Signals were linear in the concentration range studied (30 to 500 ng g^?1). Accuracy of analyses was in the order of 5% or better, with a relative standard deviation of 5%. The method could be applied to other environmental matrices: hair, urine and blood, with some modifications.